In 1874 he was invited to the Professorship of Philosophy at the University of Jena, and here he has laboured for thirty-eight years; during this period he has been listened to and admired by many of the more advanced students of philosophy of all countries and continents.
His earliest writings were historical in character, and consisted mainly of learned essays upon the classical and German philosophers.
Following upon these appeared valuable studies in the history of philosophy, which brought out, too, to some extent, Eucken's own philosophical ideas.
His latest works have been more definitely constructive.

In _Life's Basis and Life's Ideal_, and _The Truth of Religion_, he gives respectively a full account of his philosophical system, and of his ideas concerning religion.
Several smaller works contain his ideas in briefer and more popular form.
As a lecturer he is charming and inspiring.

He is not always easy to understand; his sentences are often long, florid, and complex.
Sometimes, indeed, he is quite beyond the comprehension of his students--but when they do not understand, they admire, and feel they are in the presence of greatness.

His writings contain many of the faults of his lectures.

They are often laboured and obscure, diffuse and verbose.
But these faults are minor in character, compared with the greatness of his work.